Electric tool



W. STUMPF ELECTRIC TOOL June 21 1927.

Filed March 15. 1926 2 Sheets-Sheet l W. STUMPF ELECTRIC TOOL June 21 1927. 1,633,389

Filed March 15. 1926 2 Sheets-Sheet 2 Patented June 21, 1927.

UNITED STATES PATENT OFFICE. I

WALTER STUMIPF, OI BALTIMORE, MARYLAND, ASSIGNOR TO THE BLACK & DECKER MANUFACTURING COMPANY, OF TOWSON, MARYLAND, A CORPORATION OF MARY- LAND.

ELECTRIC TOOL.

Application filed March 15, 1926. Serial No. 94,808.

The invention relates to electric tools and similar electric devices and particularly to the method of holding the stator or field in the motor casing or portion of the tool casing in which the motor is located. The in vention is illustrated in connection with a portable power driven electric tool which may be either a drill, screw driver or wrench, valve grinder or tapper, all of which are made along somewhat similar lines with variations of the mechanism to adapt it to the particular purpose in hand. The invention has particular reference to the anchoring or holdingof the field of a polyphase motor, .but can be used to advanta e with any kind of motor.

n account of the diameter and arrangement of the field the fplacing of bolts extending through the eld parallel to the axis and seated in'the casing is difiicult or impossible without increasing the outside diameter of the tool, and such bolts have been found objectionable in view of the general use of aluminum casings in such tools because the stresses resulting from the regular operation of the tools aresufiicient to break down the threads in the softer metal with the result that the screws loosen and in time the field drops on the fan with con siderable' resulting damage on account of the contact of the rapidly rotating fan with the field. The set screw method of holding the field is similarly objectionable.

The present invention relates to an improved method of anchoring or. clamping the field in such tools so as to'overcome these difiiculties obviating the necessity for screws seated in the aluminum casing to hold the field-and effecting a mounting of the field which is permanent, and which is economical not only on account of its permanency, but? as to the cost of manufacture and the space which it occupies within the casing between the field and the walls of the easing. The anchoring means alsohas the advantage that it is seated flush with the easing requiring no protruding nuts or bolt heads.

'More particularly the device of the inhaving a threaded shank which extends into a hole in the casing and is adapted to be engaged by a nut which is afiixed from outside the casing. The other end of the hook provides a shoulder adapted to engage the field, preferably the laminated portion on the side opposite to that engaged by the internal shoulder in the casing so that when the nut is tightened the field is drawn against its seat on the internal shoulders. The hooks or keys, as shown, fit in correspondingslots in the laminations of the field and one of the .hook shanks is likewise seated in a slot in the casing acting as a key to prevent rotation of the field by the reaction of the motor torque. With the keys or hooks so arranged the field may fit the casing with a very slight clearance, giving the best economy of space. I

In the accompanying drawings I have illustrated a motor stator or field anchor embodying my invention in the preferred form..

In the drawings:

Figure l is an elevation showing the gen eral layout of a portable electric tool having the motor field anchored in accordance with the method and device of the invention.-

Figure 2 is a section taken on a plane of the axis of the motor and showing the motor and field anchoring device and the portion of the tool casing which may be termed the motor casing.

Figure 3 is a section on the line 3-3 of Figure 2 looking in the direction of the arrows. I

Figure 4 is an end elevation of the casing with the handle removed and looking from the right in Figure 2.

Referring to the drawings by numerals, each of which is used to indicate the same or similar parts in the different figures, the apparatus as shown comprises the tool casing 1, the portion of the casing immediately surrounding and enclosing the motor being referred to as the motor casing 2. Within this portion of the casing I have indicated a polyphase motor 3 having shaft 4 carrying laminated rotor 5, and a stator or field 6 comprising windings 7 and laminations in the form of plate rings 8. The laminated portionof'the field is shown as of circular cross section and of a diameter to fit closely within the casing. In accordance with aptension member,

plicants practice the field has a press fit in the casing and is positioned and supported by means of inwardly projecting shoulders or flanges 10, which as shown, extend inwardly so that the diameter of the casing measured from one shoulder to the other is possibly to 4 inch less than the extreme diameter of the stator, and the shoulders 11 preferably present toward the stator a flat surface 12 at right an les to the axis, there being preferably one s oulder near the center of each of the'six sidesof the casin or if the casing is other than hexagonal, t ese shoulders may be placed to suit the structure. There is also in the form shown a filler or shoulder 27 in the corner of the easing in which filler the keyway, to be described, is formed.

The motor is inserted from the left in Figure ,2 and brought into contact with the shoulders 10 where it is held by tension members or keys shown in the form of hooks 11 and 25, each of these hooks or tension members has an abutment or offset at 14 at one end which takes over the laminations 8 at one side. As shown, said abutment is on the left side and the shank15 of the tension member extends to the right into and, in the form shown, almost through the end of the casing at 16, the casing having an openin 17 to receive the end of each shank.

e o ening counter bored, as shown at 18, to receive a field anchor nut 19 engaging the end of the which in the preferred structure is correspondingly threaded for this purpose. The nut is laced in the counter bored opening flush wath the casing.

The ends of the tension members are preferably cut short of the surface of the casing at 20 providing for the engagement of the nuts 19 by means of a suitable key referred to as a field nut key or enters the slots 21 therein.

In the form of the invention shown there are two of the tension members or hooks 11, 25, both of which are shown as passed through slots 22 in the outer cylindrical surface 24 of the field laminations. The slots and tension members are preferably parallel to the axis of the motor and rectangular, though exact compliance with these details is not essential to the successful operation of the device. One such key or tension member 25 projects into and also occupies a corresponding parallel and opposed slot 26 in the casing, the slot being located in a shoulder or filler 27, which in the form shown is formed in a corner of'the casing at the intersection of two of thefiat walls.

The manner of assembling will be understood from the descrition and drawings. The field or stator is first inserted into the casing from the left, the right hand plate or amination being brought into contact with in the aluminum body of the casing,

is preferably enlarged or a screw driver which the shoulders'lO. The nuts 17 having been removed the tension members or keys l1 and 25 are inserted from the left through and into the slots 22, one said key also occupying at the same time the slot 26 in the casing, which positions the stator and prevents a solutely an tendency to rotate as by the re action of the tor ue imparted to the rotor. The tension mem rs or keys having been placed, the nuts 20 are inserted in the counter bored holes 17 in the casing and engaged with'the threads on the ends of the keys or tension members and tightened by means of a screw driver or the like, clampin the laminations of the stator between the shoulders or offsets 14 on the ends of the keysor tension members and the shoulders 10 in the e ThlS arrangement provides a posltlve lock against the rotary tendency of the field and makes it possible to use a casing of a rela tively small diameter. It also obviates the necessity for-seating the anchoring screws doing away with the consequent tendency to release and drop the field, the hook and nuts being conveniently made as hard as may be desired so that there is no question of the threads giving away on account of the stresses incident to operation or any stress which may be applied to the motor and further these stresses are deprived of their destructive effect by the positive locking of the field.

I have thus described specifically and in detail a sin is embodiment of my motor anchor in or or that the nature and opera tion of the same may be clearly understood, however, the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention beingdefined in the claims.

What I claim and ters Patent is:

1.- The combination of a motor having a stator, a motor casing having an abutment enga ing the stator from one side, a tension member substantially Parallel to the motor axis and in the form 0 a key, the stator and easing having opposed groovesfthe key extending into both said grooves locking the stator against rotation, and having an abutment'engaging the stator oppositely to the engagement by said abutment on the casing and means for taking up on the key to grip the stator between said abutments.

2. The combination in an electric tool of a motor having a stator, a motor casing having a shoulder engaging the stator from one side, a tension member and a key, the stator and easing having opposed grooves, the key extendinginto both said grooves locking the stator against rotation, the tension member having an abutment engaging the stator op posite y to the engagement by said shoulder,

desire to secure by Let lGO and means for taking up on the tension memsion member having an abutment engaging bet to grip the stator between the abutment the stator from the other side, and means for and the tension member and the said shoultaking up on the tension member to gri the der on the casing, the casing having a destator between the abutment and the s oula pression admitting take u means to a posider, the stator having a groove and the cas- 15 tion in which it is flush with the casing. ing having an opposed groove and a key 3; In an electric tool, a tool casing, a motor en agin both grooves. fitting inside the tool casing, the motor havi e by me at Baltimore, Maryland, this ing a stator, the casing having a shoulder 5th ay of March, 1926.

l) engaging the stator from one side, a ten- WALTER STUMPF. 

